I noticed that both Canon and nikon do this and it's exclusive to their standard lenses. All the lens hoods are round and not petal shaped. Other manufacturers use petal hoods on their standard lenses so I'm guessing this is just a style choice.

I was wondering if there was any reason behind this choice or if it was just something they've done forever

Actually hoods for wide angle lenses tend to be petal-shaped, as that's a better design for them (and it's not needed with normal/telephoto lenses, where the AoV is narrow enough that a round hood does the job). But since hoods for zooms must be optimized for the wide end (except in the case of the reverse zoom found on the original 24-70mm), because they'd vignette at the wide end if they worked well on the tele end, those hoods tend to be petal-shaped. Even the 24-70 hood has a petal shape for the wide end, it's just much deeper because of the reverse zoom (meaning it works well at all focal lengths, unlike the hoods for all other extending zooms).

Technically (IIRC, epsiloneri pointed this out in a previous thread), a petal design would be optically best for any focal length lens, but practically speaking for normal and longer lenses, round is just as good (because of the AoV is small enough relative to the front element size), and allows the lens to be set hood-down more safely.

dok

Some possible reasons for non petal shaped lens hoods :- the lens hood has to be screwed to the lens. Depending on the thread, petal shaped one could get in the way.- the lens as a front focusing element which rotates while focusing.

lonebear

Just want to add one point. A petal shaped hood requires the cutback portion of the hood to be aligned with the corners of the frame. If the hood is not clicked onto its designed position you may see your hood in your picture.

Just want to add one point. A petal shaped hood requires the cutback portion of the hood to be aligned with the corners of the frame. If the hood is not clicked onto its designed position you may see your hood in your picture.

Yes, happens with my 35 and 24mm lenses. With the 8-15mm you have to remove the hood at the wide end. What is the cut off for petal hoods for crop?